1. Field of the Invention
The subject invention relates to valves and, more particularly, to check valves for use in controlling flow of fluids.
2. Description of the Invention Background
Over the years, a variety of different valves have been developed for controlling fluid flow through pipelines. Most valves, regardless of type, comprise a housing member that operably supports a flow control member therein. The housing typically has two or more ports that are constructed for attachment to corresponding portions of pipelines. Some ports are provided with threaded connections, while others utilize a "slip fit" connection wherein a section of pipeline is slidably received in a socket formed in the valve housing. The pipe is typically retained within the socket by an appropriate attachment medium or adhesive. For example, the pipe may be affixed to the socket by welding, soldering, gluing, etc.
The flow control characteristics afforded by a valve are generally dependent upon the type of flow control member employed. In many pipeline applications, it is desirable to utilize valves that only permit fluid to flow in a single direction. In those instances, valves known as "check valves" are usually employed. For example, many municipal water authorities require each user to employ a device for preventing fluid from their respective plumbing system from flowing into the potable water supply. When water pressure in a potable water system is unusually low, or if high pressure occurs in the user's plumbing system, reverse flow from the user's plumbing system into the potable water supply is possible. Such reverse flow or "back flow" could contaminate the water supply. In these applications, check valves are typically attached at or near the location where the consumer's plumbing system connects to the common supply line. Of course, the use of check valves is not limited to drinking water applications. Check valves are also employed in a variety of other residential and industrial applications where such unidirectional flow characteristics are desirable.
A number of differently configured check valves exist for maintaining unidirectional fluid flow within a pipeline system. One type of check valve, known as a "ball" check valve, employs a ball-shaped flow control member that is movably supported within the valve housing and is adapted to sealingly engage a seat adjacent one of the ports. When fluid flows into the valve housing in one direction, the ball is forced out of contact with the seat and the fluid is permitted to pass through the valve. If the fluid attempts to flow through the valve in an opposite direction, the fluid forces the ball into contact with the seat to thereby prevent the fluid from flowing back through the valve.
Another type of check valve, known as a "swing" check valve employs a disc that is pivotally attached to the valve housing and is adapted to sealingly engage a valve seat that surrounds one of the valve ports. When fluid flows through the housing in a desired direction, the disc is forced out of contact with the seat by the fluid and the fluid is permitted to flow through the valve. Should the fluid attempt to flow back through the valve, however, the back-flowing fluid will pivot the disc into contact with the seat to seal off that port. Thus, the fluid is prevented from flowing in reverse direction through the valve.
While such valves can effectively limit flow to a single direction through a pipeline, such prior check valve designs have various shortcomings. For example, if the valve disc is not achieving a seal with the seat or the disc is otherwise damaged or it becomes desirable to limit the flow of fluid within a pipeline in another direction, the prior check valve arrangements must be detached from the pipeline and a new valve must be installed. To install a new valve, the flow must be discontinued and the fluid is typically drained from the pipeline. If a hazardous fluid is being handled, special precautions must be taken to prevent environmental contamination and injury to the personnel installing the valve. If the old valve has been installed by welding or by gluing, the old valve usually must be cut from the pipeline. Often times when a valve is cut from the pipeline, an additional section of pipeline must be added to compensate for the section(s) of pipe that were removed with the old valve. The reader will readily appreciate that such activities can be very time consuming and costly in the form of labor expenses and process downtime, depending upon the application.
Also, in many pipeline arrangements, it is desirable to monitor the performance of the valve disc during use to determine whether it is functioning adequately. In prior valve designs, however, the entire valve must be removed from the pipeline or a cover member must be detached from the valve housing to permit the disc to be viewed. Thus, personnel are unable to view the disc when fluid is flowing through the valve or when the disc is seated in a sealing orientation. In addition, many check valves employ a single seal arrangement that can result in an inadequate seal.
Thus, there is a need for a check valve that has a flow control member that can be repositioned within the valve housing without removing the valve from the pipeline in which it is installed.
There is a further need for a check valve that has a seal disc therein that can be inspected while in a sealing position and when fluid is flowing through the valve.
There is still another need for a check valve that has an improved seal arrangement.
Another need exists for a check valve disc arrangement that has the above-mentioned characteristics that can be retrofitted into other valve bodies without removing the valve body from a pipeline.
Yet another need exists for a check valve with the above-mentioned characteristics that has two, three, or four or more ports therein.